For the purposes of this specification, the terms set out below are defined as follows.
The term “post weld treatment heating” refers to the operation of post weld heating a section of pipe to the desired temperature after performing a welding operation upon a section of pipe. For example, in a post weld heating operation using P91 chrome-moly steel pipe, the pipe is heated to a temperature range between 200-1015 degrees Fahrenheit. The term “P91” is used to describe a common type of pipe used in a high-pressure application for transporting oil, gas, or steam. P91 is comprised of a chromium-molybdenum alloy having the chemical composition of 9Cr-1Mo—V (P91).
The term “hydrogen bake-out” refers to a finishing operation on a weld whereby a welded section of pipe in-situ is held at a constant temperature in order to remove any hydrogen impurities from the weld in preparation for a cutting or welding operation. A hydrogen bake-out helps prevent the weld-joint from pre-mature fracturing of the weld-joint or pipe in-situ.
The term “interpass temperature” refers to the temperature of the pipe between welding passes. A “welding pass” is the path taken by a single welding operation. For example, a welding pass for a section of pipe is the circumferential path taken around a weld joint for the pipe.
Many of the prior art inventions for heating pipe are difficult and cumbersome to apply, remove or relocate from the weld area, which typically may be held within a tightly confined area. Additionally, many of the prior art inventions require a power source requiring the use of heavy machinery to provide a suitable source of power. For example, a generator truck is typically required for voltage requirements exceeding 480-600 volts. Each truck uses heavy cabling to supply power from the generator mounted on the truck to the heating apparatus, which is typically located in a remote location from the weld site. The heavy cabling may present a hazard at the work site since the use of heavy voltage cabling present a safety hazard.
It is, therefore, desirable, to provide a portable heating apparatus for heat treating a section of oilfield pipe that is easy to use and that does not pose a worksite safety hazard.